The present invention relates to an NC (Numerical Control) system, and more particularly to a graphics display unit for such an NC system.
NC systems control the position of a tool with respect to a workpiece according to numerical information indicative of the tool position for machining the workpiece. Such NC systems can machine workpieces of complex shape easily and highly accurately and increase the rate of production.
Graphics display units associated with the conventional NC systems display the current tool position, the machining path of the tool, machining information of the workpiece and other parts, for checking a machining program and monitoring machining conditions. Such a graphics display unit will be described with reference to FIG. 1 of the accompanying drawings.
In FIG. 1, a tool tip mark 11 at a program original point Q.sub.0 is indicative of the position of a tool and can be moved by entering movement information to erase a currently displayed tool tip mark 11 and display a new tool tip mark 11 at new coordinates. The types of movement between the new and old coordinates can be displayed according to the line type (cutting feeding is indicated by the solid lines 1 and positioning by the dotted lines 2 in FIG. 1). As a result, paths of movement of the tool are displayed as shown in FIG. 1 for enabling program checking and machining condition monitoring. Denoted at 3 in FIG. 1 is the base line.
The conventional graphics display unit thus constructed has suffered the following disadvantages:
1) Since the tool tip mark 11 indicative of the current tool position is symbolically displayed, it is not possible to determine whether the tool tip interferes with a workpiece 10 and holder mechanisms such as a tailstock and a chuck (not shown).
2) With the tool tip mark 11 moved in the foregoing manner, the tool tip mark 11 momentarily disappears from the graphics display unit, and appears to flicker while it is moving.
3) The display of a workpiece shape and cutting paths in superposed relation allows determination of which portion of the workpiece shape is to be machined. When cutting paths become complex, they sometimes are displayed as being superposed on themselves, and cannot easily be confirmed.